596 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



compared with the total length, 205; the proximal 

 measurement across the tuberosities is 49, while the 

 measurement of the head to the front of the great 

 tuberosity is 67; the moderately prominent deltoid 

 crest extends 88 millimeters below the head, and the 

 supinator ridge rises 60 millimeters above the interior 

 border of the radial trochlea. 



The femur (fig. 500) has only partly assumed the 

 distinctive titano there family characters; the shaft has 

 not yet flattened; it more closely resembles that of 



below the trochanters, by the elevated patellar facet 

 facing anteriorly and inferiorly. 



Pelvis of Eotitanops borealis (neotype) 



The proportions of the left innominate bone pre- 

 served in the neotype of Eotitanops horealis (Am. Mus. 

 14887) indicate a subcursorial type of pelvis, slen- 

 derly buUt, with the following characters: (1) Neck 

 of ilium relatively narrow (tr. 29 mm.); (2) tuber- 

 coxae and external border of ilium partly concave; 

 (3) pubo-ischiadic fenestra elongate or vertically 



i ma/ 



Figure 500. — Humerus and femur 

 Eotitanops princeps 



Am. Mus. 296, Wind River. Right humerus (Ai, A2) 

 andtemur (B) of type. One-third natural size. 



other subcursorial Eocene perissodactyls, such as 

 Hyrachyus, rather than the mediportal middle Eocene 

 forms. Among the middle Eocene titanotheres its 

 closest resemblances are to the femur of MesatirMnus. 

 The head is lacking. From the great trochanter to 

 the bottom of the internal condyle the shaft measures 

 250 millimeters. The bone is further distinguished 

 from that of some of the more recent or middle 

 Eocene titanotheres by the laterally compressed and 

 deeply recurved great trochanter, by the very promi- 

 nent second trochanter, by the lateral compression or 

 convexity of the shaft anteriorly between the trochan- 

 ters, a character which it shares with MesatirMnus, 

 by the flattening of the shaft posteriorly between and 



Ai 



Figure 501. — Pelvis of Eotitanops borealis 



A, Am. Mus. 148S7' (neotype), incomplete pelvis associated with skull, ventral 

 (Ai) and outer side (A2) views; B, Am. Mus. 14888, fragment of left ilium, 

 indicating a somewhat wider ilium than that in the preceding specimen, asso- 

 ciated with teeth and other parts, ventral view. One-third natural size. 



compressed; (4) plane of ilium at angle to that of 

 pubis; (5) proportions of subcursorial rather than of 

 mediportal type. 



Pes of Eotitanops 



The pes as compared with those of the other lower 

 Eocene Perissodactyla (fig. 502) — namely, Eohippus 

 (Equidae) and Heptodon (Lophiodontidae) — again 

 exhibits Eotitanops as approaching the relatively large 

 and slow-moving perissodactyls of the period, although 

 possessing many characters in common with the con- 

 temporary lighter-limbed forms. 



In the comparative outlines of Figure 502 it wUl 

 be observed that Eotitanops horealis stands midway 



